We begin this week ….  

צַ֤ו אֶֽת־אַהֲרֹן֙וְאֶת־בָּנָ֣יו לֵאמֹ֔ר זֹ֥את תּוֹרַ֖ת הָעֹלָ֑ה הִ֣וא הָעֹלָ֡ה עַל֩ מוֹקְדָ֨הֿ עַל־הַמִּזְבֵּ֤חַכׇּל־הַלַּ֙יְלָה֙ עַד־הַבֹּ֔קֶר וְאֵ֥שׁ הַמִּזְבֵּ֖חַ תּ֥וּקַד בּֽוֹ׃ 

Command Aaron and his sons thus: This is the ritual of the burnt offering: The burnt offering itself shall remain where it is burned upon the altar all night until morning, while the fire on the altar is kept going on it. 

וְלָבַ֨שׁ הַכֹּהֵ֜ןמִדּ֣וֹ בַ֗ד וּמִֽכְנְסֵי־בַד֮ יִלְבַּ֣שׁ עַל־בְּשָׂרוֹ֒ וְהֵרִ֣ים אֶת־הַדֶּ֗שֶׁן
אֲשֶׁ֨ר תֹּאכַ֥ל הָאֵ֛שׁ אֶת־הָעֹלָ֖ה עַל־הַמִּזְבֵּ֑חַ וְשָׂמ֕וֹ אֵ֖צֶל הַמִּזְבֵּֽחַ׃ 

The priest shall dress in linen raiment, with linen breeches next to his body; and he shall take up the ashes to which the fire has reduced the burnt offering on the altar and place them beside the altar.   

The Keli Yakar Writes: The Torah mentions ashes in this context because the rectification for arrogance is ashes, i.e., one should say, “I am dust and ashes,” like Avraham. This causes that he will be elevated to great heights, for anyone who lowers himself is lifted up by Hashem. Thus, the kohein making the atonement wears these two garments: The linen garment, according to his size, and not too big — to hint that one should not behave in a manner beyond his level. Secondly, the linen pants, which atone for the transgression of illicit relations, which he needs if he was arrogant, as Chazal said (Sotah 4b): Anyone who is arrogant is considered as if he transgressed all the illicit relations. The ashes are placed next to the altar, which represents humility.   

Rabbeynu Bachya Writes: ולבש הכהן מדו
בד ומכנסי בד ילבש על בשרו והרים את הדשן, “The Priest shall put on his fitted tunic and he shall put on linen trousers on his flesh; he shall remove the ash.” The Torah here teaches that even such a seemingly inconsequential activity as removing the ash from the altar is considered as part of the sacrificial service. Were this not so it would not be necessary for the Priest to don the garments reserved for performing service in the Temple or Tabernacle.